Monticello nuclear plant upgrade costs double

The utility revealed the cost in a filing Wednesday with the state Public Utilities Commission, after previously saying the figure was a trade secret.

The project was originally expected to cost $320 million. The recently completed five-year project included replacement of aging equipment and boosting electricity output by 12 percent. The upgrades are intended to extend the life of the 43-year-old reactor another two decades.

Xcel expects to restart the plant this month after a four-month shutdown.

The utility has asked the PUC for a rate hike for 1.2 million Minnesota customers because of the cost overruns, which it blames on the complexity of the project. The commission is expected to decide this fall.